Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$217.48	13.636%	$247.1356	$247.14	$247.15	$247.10
Purchase #2	$48.50	4.168%	$50.5215	$50.52	$50.50	$50.50
Purchase #3	$215.43	3.170%	$222.2591	$222.26	$222.25	$222.30
Purchase #4	$27.30	12.463%	$30.7024	$30.70	$30.70	$30.70
Purchase #5	$187.51	10.342%	$206.9023	$206.90	$206.90	$206.90
Purchase #6	$119.88	11.216%	$133.3257	$133.33	$133.35	$133.30
Purchase #7	$188.82	11.228%	$210.0207	$210.02	$210.00	$210.00
7 purchase totals =	$1,004.92		$1,100.8673	$1,100.87	$1,100.85	$1,100.80